This invention relates to athletic shoes, and, more particularly, to an athletic shoe which includes a spring in the heel portion of the sole.
Various attempts have been made to provide athletic shoes with shock absorbing or energy storing devices such as resilient materials and springs. A shock absorbing material cushions the shock of the foot striking the ground. Some shock absorbing materials absorb energy and dissipate it as heat. The athlete therefore loses a portion of his kinetic energy every time his foot strikes the ground. An energy storing device stores energy as the foot strikes the ground and returns energy to the athlete as the foot leaves the ground.
The cushioning or energy storing device should be confined within the sole, but the height of the sole should be maintained within certain desired limits. In other words, the sole should not be excessively thick. The height or thickness constraint has limited the effectiveness of previous cushioning and energy striking materials.
The energy storing device should also be light weight. Some prior attempts to provide energy storing devices in shoes have resulted in shoes which were too heavy. For example, dress shoes and work shoes have been provided with steel springs, but steel springs are too heavy for athletic shoes such as tennis or basketball shoes.